In the present case, the expression “adjusting element” is to be understood comprehensively. It includes rear hatches, rear lids, engine hoods, doors, in particular side doors, trunk compartment floors or the like of a motor vehicle.
Primarily, however, the drive arrangement in question is used in rear hatches and side doors of motor vehicles. It serves for the motorized adjustment of the respective adjusting element in the closing direction and in the opening direction. It is important here as a rule that, in addition to the motorized adjusting operation, the drive arrangement also permits manual adjusting operation. Furthermore, it is important here that the respective hatch or door position is held reliably in the case of a power failure, in order to avoid hatch or door movements which are unexpected and therefore dangerous to the user.
The known drive arrangement (WO 2007/014686 A1), from which the invention proceeds, is equipped with a clutch arrangement which is connected into the power train with a drive connection and a driven connection, which is a wrap spring arrangement. The wrap spring arrangement forwards a movement which is introduced on the drive side to the drive connection and brakes a movement which is introduced on the output side, with the result that the rear hatch can be held reliably in every intermediate position. The known drive arrangement with a wrap spring arrangement is of structurally simple and robust construction. In the case of a suitable design of the wrap spring, satisfactory switching behavior can be achieved with regard to the switchover between drive operation and braking operation.
Clutch arrangements which forward a movement which is introduced on the drive side to a drive connection and block movements which are introduced on the output side are also known from the prior art (DE 195 81 436 C1). Locking mechanisms of this type are equipped with three pairs of clamping roller freewheels which operate in opposite directions. Braking operation in the above sense cannot be realized by way of clamping locking mechanisms of this type.
The invention is based on the problem of configuring and developing the known drive arrangement in such a way that the switching behavior is improved with regard to the switchover between drive operation and braking operation.